1. Technical Field
The present invention pertains to improvements in methods and apparatus for producing surgical sterile slush. In particular, the present invention is an improvement of the methods and apparatus disclosed in U.S. Pat. No. 4,393,659 (Keyes et al). The disclosure in that patent is expressly incorporated herein in its entirety by this reference.
2. Discussion Of The Prior Art
The Keyes et al patent discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the exterior of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located in the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons, are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid such as alcohol or glycol serving as a thermal transfer medium between the two basins. A sterile sheet of material impervious to the thermal transfer medium is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to scrape congealed sterile material from the product basin side to thereby form a slush of desired consistency in the product basin.
As noted in U.S. Pat. No. 4,934,152 (Templeton), the above-described system has a number of disadvantages. Specifically, the separate product basin must be removed and re-sterilized after each use. In addition, the glycol or other thermal transfer medium is typically highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterilized drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped off the sides of the conformed drape receptacle to form the desired slush.
While the Templeton approach solves the aforesaid problems associated with the Keyes et al system, it requires the user to purchase an entirely new system. It is desirable that the aforementioned problems be addressed in the context of existing systems constructed in accordance with the Keyes et al patent. However, if one attempts to eliminate the product basin and the requirement for a thermal transfer medium from the Keyes et al system by merely using a drape as proposed by Templeton, more often than not the drape is ripped by the basin spacers projecting from the heat transfer basin. The spacers are permanently secured to the basin wall and include sharp or abrupt annular edges that tend to tear or snag or slice the drape, particularly during stirring.